Probing the ultrafast dynamics of salts in condensed and aqueous phases
Abstract/Contents
- Abstract
- The movement of molecules through a condensed phase is governed by an extremely complex hierarchy of considerations and constraints on motion. This is particularly true when electric fields from ions and hydrogen bonding is involved, let alone heterogeneous structuring of the liquid. This thesis seeks, principally, to quantify the timescales of probe molecule motions and to then improve the understanding of how these motions occur. The ultimate goal is to predict how changes in the environment will affect motion both of the liquid and any dissolved solutes. The nature of molecular motions in the condensed phase was investigated using ultrafast two-dimensional infrared spectroscopy. This enabled non-perturbative interrogation of the systems in question as well as the time resolution necessary to detect changes in motion. Both the reorientation of the molecules and the spectral diffusion (which quantifies structural fluctuations) were used to better understand the motions in a number of chemical systems, focusing on the effect of salts. Both aqueous solutions of salts and room temperature ionic liquids (which are a subset of salts that remain molten at room temperature) with dissolved solutes were investigated. A number of noteworthy results were obtained and some interesting conclusions were drawn about aqueous salt solutions. It was found that, in water, some salts (particularly those with a high charge density) can slow the movement of water molecules considerably. This is primarily dependent on the anion, to which the water is directly hydrogen bonded, but the cation can play a role. However, certain salts (including borohydride) leave the dynamics of water unperturbed even when extremely concentrated. This is facilitated by the formation of hydrogen bonds with water molecules such that the hydrogen bond network remains fairly intact despite the presence of the ions. The structuring of the liquid may also play a role -- ionic liquids, which exist as liquids even without the addition of water and have internal structuring, have different dynamics than typical salts when the same amount of water is added to both. Studies were conducted on ionic liquid solutions to determine the effect of structuring. By changing the alkyl chain length of the cation, the ionic liquid adopts different configurations. This cause the dynamics of solutes to change in ways that would not necessarily be expected given the change in bulk properties like viscosity. The region of the ionic liquid that is solvating the probe molecule is found to determine the dynamics rather than the liquid as a whole. However, as was found with dissolved carbon dioxide as it is of note for carbon capture applications, the long range structuring of the ionic liquid can play a role for a subset of the motions that the probe experiences.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Giammanco, Chiara |
|---|---|
| Associated with | Stanford University, Department of Chemistry. |
| Primary advisor | Fayer, Michael D |
| Thesis advisor | Fayer, Michael D |
| Thesis advisor | Dai, Hongjie, 1966- |
| Thesis advisor | Moerner, W. E. (William Esco), 1953- |
| Advisor | Dai, Hongjie, 1966- |
| Advisor | Moerner, W. E. (William Esco), 1953- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Chiara Giammanco. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Chiara Helena Catherina Giammanco
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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